Exhaust Gas Recirculation

The ECM controls ported vacuum to the EGR valve with a solenoid valve. The ECM uses coolant temperature, throttle position and manifold pressure to control vacuum solenoid operation. During cold engine operation and idle, the solenoid valve is grounded by the ECM. This blocks vacuum to the EGR valve. During warm engine operation and off idle speeds, the solenoid is not grounded and vacuum opens the EGR valve.